Resiliently coupled drill bit



April 3, 1956 J. E. ORTLOFF 2,740,651

RESILIENTLY COUPLED DRILL BIT Filed March 10, 1951 Uohn. E. Orloff (Envenbor (lbborrzeg United States Patent RESILIENTLY COUPLED DRILL BIT John E. Ortlofl, Tulsa, Okla., assignor to Esso Research and Engineering Company, a corporation of Delaware Application March 10, 1951, Serial No. 214,993

Claims. (Cl. 287-85) In present day drilling, a large proportion of the holes that are bored into the earth for the production of crude petroleum from underlying oil bearing strata are made by what is known as rotary drilling. The drilling is accomplished by mounting a suitable drill bit on the lower end of a drill pipe which extends the full length of the hole, the drill pipe and drill bit being rotated to accomplish the drilling by a combination of scraping, grinding and percussion forces which break up the rock and related material. In order to provide for removing the cuttings and to seal the hole against the loss of gases and liquids encountered, a drilling fluid is circulated down through the drill pipe and back through the annulus between the drill pipe and the walls of the bore hole.

In rotary drilling practice many different types of bits are employed in order to provide for the greatest efliciency in cutting up the various types of formations that are: encountered during the making of the hole. Ordinarily drag. bits or fishtail bits are useful when drilling through whatare known as soft formations such as loosely cemented sands, shales and clays. When harder rocks are encountered such bits dull quite rapidly and drilling progress is slow. Hence, when harder formations are encountered; it. is general practice to pull the drill string and change to what are known as rock bits in which cones or rollers are employed. It has occurred to drilling operators that it. were possible to use diamonds or similar altrasiveson a drag bit the drag bit could be used to drill both soft and hard formations, which would result in a saving of time required to make a round trip with the 'drill string=inorder to change bits.

However the use of diamonds or similar material in drag bits has not been at all successful in the past because of the fact that the impact shocks normally encountered in drag bit drilling tend to shatter the diamonds or at least jerk them from their setting.

It is an object of the present invention to provide a drill bit assembly that enables a bit to be flexibly or resiliently attached to a drill string so as to permit a full compressional load on the bit and yet absorb the shock loads inherent in drag bit drilling.

It is a further object of the invention to provide a flexible coupling assembly for drag bits, and especially for drag bits carrying particles of abrasive materials such as diamonds on the working edges, so as to enable the bit to drill effectively through virtually any type of formation encountered in drilling.

In accordance with this invention a drill bit is provided having a coupling comprising a threaded adapter which screws onto the end of a conventional drill string and which is provided with splines that fit into cooperating splines in the top of the drag bit with sufficient clearance so that the space thus provided can be filled with iii iii

2,740,651 Patented Apr. 3, 1956 rubber or similar resilient material which may be bonded to the surfaces it contacts and provide shock absorption for the bit. The relationship between the depth of the splines and the thickness of the resilient material between the splines must be such as to ensure that the resilient material will always be in compression when the bit is rotated. Preferably, means are provided for preventing Wear that is apt to occur between the bit and the coupling as well as means to prevent access of drilling fluid to the splined portion to avoid pressure loss or other deleterious effects brought about by contact of the fluid with the area in which the resilient material is retained.

The nature and objects of the invention will be more fully understood from the ensuing description and from the accompanying drawing in which Fig. 1 is an elevational view, partly in section, of one embodiment of a drill bit and coupling assembly constructed in accordance with this invention;

Figure 2 is a sectional view taken on line 11-11 of Figure 1;

Figure 3 is a bottom view of the assembly of Fig. l; and

Figure 4 is an elevational view corresponding to Figure 2 and showing an alternative arrangement of abrasive particles on the bit.

Referring to the details of the drawing, it will be seen that the coupling member consists essentially of an adapter, the upper section 11 of which is threaded so that it can be screwed on to the end of a. drill string. The intermediate section 13 of the adapter is provided with a plurality of circumferentially spaced splines 14 arranged lengthwise of the adapter. The adapter terminates in a lower essentially cylindrical section 15. A fluid passageway 12 passes through the whole length of the adapter.

The drag bit is of essentially conventional shape and consists of an upper shank portion 17, a generally cylindrical body portion 18, and flat blade members 19. The bit shank 17 is provided with an elongated recess having splines 22 that correspond in shape to the splines 14 of the adapter. It will be noted that the splines 14 and splines 22 are all of essentially square or rectangular cross-section. Thus when the splined section of the adapter is inserted into the splined section of the bit shank the splines will define between them an annular space of tortuous cross section. The body of the bit is provided with a cylindrical recess 26 of such diameter that the lower cylindrical portion 15 of the adapter will fit into it with a minimum amount of clearance. The annular space between the splined members is filled with rubber or similar resilient material 23. Preferably a free space 25 is provided below the splined section to provide for expansion of the resilient material.

The cylindrical recess 26 terminates in an enlarged recess 27 which communicates with fluid nozzles 28 so that drilling fluid may pass down through passageway 12, recess 27 and nozzles 28 to form jets of fluid that will aid in drilling.

In assembling the bit and adapter the resilient material 23 will be preshaped to correspond to the general outline of the annular space between the splined members and inserted into the bit shank, after which the adapter member will be inserted and the resilient material bonded to the surfaces it contacts, by heating in accordance with usual techniques. The lower cylindrical section 15 of the adapter and the cylindrical recess 26 will serve to center the adapter properly during assembly. Furthermore, the cylindrical members will serve as a bearing for the slight rotational twist that will occur between the bit and the adapter during use. To ensure that the drilling fluid will not come into contact with the resilient material in the splined section, it is preferred that annular grooves 29 be provided in the body of the bit adjacent the cylindrical recess 26, and O-ring seals or gaskets 30 to be fitted into the grooves 29. Preferably a thrust bearing 32, made of high grade bronze. for example, is inserted between the shoulder 33 of the adapter 11 and the shoulder 34 on the top of the bit shank 17 to prevent or take up wear caused by the slight rotational movement between the adapter and the bit when the bit is in use.

Obviously the improved adapter and bit arrangement of this invention may be used for taking up shocks in ordinary drag bits or in any other type of rotary bit. In the preferred embodiment of the invention, however, a drag bit member is employed and is provided with abrasive particles on the leading edges of the bit blades. These may be in the form of inserts of diamond impregnated material 20, for example, as shown in Figs. 1 and 3, or alternatively the entire leading edge may carry a diamond impregnated matrix 21 as shown in the fragmentary view, Fig. 4.

It is of course well known to employ resilient layers of one sort or another to protect working parts against vibration and excessive strain. In the present invention, however, although the torque in the drill string is transmitted to the bit through the resilient material 23 the amount of torque which can be applied to the bit is not limited by the shear strength of the material. The rubber or other resilient material serves only to cushion the shock from the bit during drilling and does not govern the amount of torque that can be transmitted to the bit. The free space 25 is important in that it provides for expansion of the rubber so that it will maintain its resilience under compression.

Another important feature of the invention is that the splines 23 on the bit must be deep enough and the splines 14 on the adapter must be high enough to ensure that the bonded resilient material 23 will always be in compression when the bit is rotated. It may be stated that for best results the thickness of the resilient material 23 between the major diameters of splines 14 and 22 as well as the thickness between the minor diameters of the splines should not be greater than A the maximum height of the splines. Likewise, the thickness of resilient material between mating splines 14 and 22 should not be greater than A the maximum width of the splines.

It is to be fully understood that this invention is not to be limited by the specific embodiments described above, for various changes and modifications thereof may be made without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A bit assembly for the drilling of bore holes in the earth comprising an essentially tubular adapter member having an upper section attachable to the lower end of a drill pipe, an intermediate section provided with a plurality of circumferentially spaced splines of essentially rectangular cross-section arranged lengthwise of the adapter and a lower essentially cylindrical section, a generally conventional bit member provided at its upper end with a splined bore corresponding in general shape to said splined intermediate section of said adapter member, said bore terminating in a cylindrical section, said adapter member fitting into said bore in said bit member so that said adapter cylindrical section fits with minimum clear ance into said bit cylindrical section and said splines of said bit member and of said adapter member define be tween them an elongated annular space of tortuous cross section, and resilient material filling said annular space and bonded to the surfaces of said splined section and said splined bore.

2. Assembly according to claim 1 in which said splined section annular space terminates in a free space into which said resilient material will expand under com pression.

3. Assembly according to claim 1 in which the maximum thickness of the resilient material in said annular space between the major diameters and between the minor diameters of the splines in the adapter member and the bit member is not greater than A the maximum height of the splines.

4. Assembly according to claim 1 in which the maximum thickness of the resilient material between mating splines is not greater than fit the maximum width of the splines.

5. Assembly according to claim 1 in which at least one annular groove is provided in at least one of said mating cylindrical sections adjacent its area of contact with the other of said mating sections, and including gasket material filling said annular groove.

References Cited in the file of this patent UNITED STATES PATENTS 741,150 Long Oct. 13, 1903 1,513,649 Standlee Oct. 28, 1924 1,687,019 Halberg Oct. 9, 1928 1,706,072 Rieger Mar. 19, 1929 1,923,487 Howard et al. Aug. 22, 1933 1,923,488 Howard et al. Aug. 22, 1933 1,946,956 Waseige Feb. 13, 1934 2,068,474 Schwinn Ian. 19, 1937 2,150,189 Ronneberg Mar. 14, 1939 2,259,460 Dexter Oct. 21, 1941 2,560,644 Hartzell July 17, 1951 2,571,802 Wilfiey et al. Oct. 16, 1951 FOREIGN PATENTS 827,277 Germany Ian. 10, 1952 

